Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the read-only nature and potential incompleteness. The description adds value by noting the response is a list and advising pagination via cursor. This goes beyond the annotations without contradicting them, providing helpful runtime behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two short sentences with no redundancy. The core action ('List posts from a Facebook group by group URL') is front-loaded, and the pagination note is concise. Every word contributes meaning.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description states the return type (a list) and pagination mechanism, which is sufficient for an agent to correctly invoke the tool. While it does not detail the post object structure, the absence of an output schema and the simplicity of the tool make this acceptable. It is complete enough for correct use.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema provides 100% coverage for all three parameters (url, cursor, sortBy), including detailed descriptions and an enum with explanations for sortBy. The tool description adds no additional parameter semantics beyond what the schema already offers, so it meets the baseline without excelling.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states the verb 'List', the resource 'posts from a Facebook group', and the input 'by group URL'. It clearly distinguishes this tool from siblings like facebook_group_get (which retrieves group info) and facebook_profile_posts_list (which lists a profile's posts). The phrase 'Returns a list (use cursor when paginated)' further specifies output type.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides basic usage (list posts by URL) but does not explicitly mention when to use this tool over alternatives or any exclusions. While the name and description make the use case obvious, there is no guidance on when not to use it or how it differs from related list tools. This leaves some inference to the agent.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.